This invention relates to automatic chemical testing apparatus and more particularly to means for providing sample aliquots to reaction containers.
The present invention contemplates improvement in the type of automatic chemical testing apparatus disclosed in U.S. Pat. No. 3,728,079 issued Apr. 17, 1973 to John J. Moran and assigned to the assignee herein, the disclosure of which is incorporated herein by reference. More particularly, the present invention contemplates an improvement in the type of sample fluid dispensing means in such automatic chemical testing apparatus disclosed in U.S. Pat. No. 3,716,338 issued Feb. 19, 1973 to John J. Moran also commonly assigned and incorporated herein by reference. In chemical testing apparatus of the type contemplated herein, a sample, for example human serum, is provided at a sample source, and aliquots of the sample are dispensed into individual reaction containers, each reaction container being utilized for determination of the concentration of a different substance in the sample. The reaction containers are indexed through successive positions for incubation and addition of reagents thereto, and the reacted contents of each reaction container are withdrawn for analysis by readout means such as spectrophotometric analysis means and associated signal translation and printout for display circuitry.
Necessary attributes of a successful system include ability to deliver aliquots from successive samples without intersample contamination, ease of fluid handling and in improved forms, speed of the dispensing operation. It is desirable to reduce the length of conduits through which samples run past compared to, for example, the type of apparatus disclosed in U.S. Pat. No. 3,799,744 to Jones. Further, it is important to select a reduced amount of sample to be withdrawn from a sample source if desired, since the amount of sample available is generally limited.